Apparatus for and process of reduction of finely-divided material



1, 1 ,2 5 March 1, 1927. w. GARDNER 6 9 9 APPARATUS FOR .AND PROCESS OFREDUCTION OF FINELY DIVIDED MATERIAL Filed April 14, 1926 INVENTOR Q /MW W flZZ/x Patented Mar. 1, 192' 7.

UNITED, STATES PATENT- oFFlcE.

WILLIAM GARDNER, or CLEVELAND, OHIO.

APPARATUS r03 AND rnocnss or nn-noo'rron or FINELY-DIVIDED MATERIAL.

Application filed April 14, 1926. Serial No. 101,871.

This invention relates to the process of obtaining and separating finelydivided granular material by what is known as a dry grinding process asdistinguished from 6 a wet grinding process for thesame purpose.

not require expensive apparatus and ma-i chinery, and which eliminatesthe use of 1 screens and numerous conveyors and which has comparativelyfew parts to wear or get out of order. 1

A further object of the invention is to provide a process for separatingfinely di- 2 vided material in which the fines are removed from thegrinding unit as made thus preventing the cushioningof the ungroundmaterial within the grinding unit.

Further and more limited objects of my 2 invention will appear as thedescription proceeds and by reference to the accompanying drawing inwhich is disclosed a somewhat diagrammatic view partly in section andpartly'in front elevation of the apparatus used In connection with myprocess.

In the accompanying drawing I have disclosed a short type pebble mill 1which is fed from a hopper '2. The material is ground or crushed in thepebble mill 1 and connected with the pebble mill is a conduit 3 which isconnected with the top of a settling and classifying chamber 4 havingbaflles 5 and 6 adjacent the inlet. Below the chamber 4 are a pair ofconveyors 7 and 8 which are driven in opposite directions as indicatedby I the arrows. The settling chamber is also provided with a pluralityof spouts 9 having valves 9 through which the material may be withdrawnand tested. The spouts 9 are so constructed that they may be positionedto deliver material either to the conveyor 7 which returns the oversizematerial to the grinding unit or to the conveyor 8 which removes thefinished product. Connected to-the upper end of the settling chamber isa conduit 10 having apairof diverging delivery branches 11 and 12 de-'livering to the lower end of a. filter chamber 13. The filter chamber 13is an air filter of standard type having flat screens or bags. Connectedwith the upper end of the filter chamber 13 is a suction fan 14 drivenby a variable speed motor 15.

The material tobe ground is delivered into the hopper 2 and thence intothe pebble mill and the fines are removed as soon as formed. It has beenfound by experiment that the greater partof the grinding in the usualtype pebble mill is accomplished in the first .five feet'of the mill andconsiderable power is wasted due to the cushionin 'action' of the finelydivided particles on t e oversize or unfinished product within. themill. According to my process I make use of a short type of ball orpebble mill and remove the fines as soon as formed. This is accomplishedby an adjustable current of air through the grinding machine, the;velocity of the air being suohgtha-t the fine particles are held insuspension thus preventing the cushioning of the unground materialwithin the pebble mill. This current of air may be adjusted so that aclassifying of the different size particles will result as onlyparticlesof the required size are removed from the grinding unit. Thepebble mill is also provided with an adjustable air inlet opening shownat-16 whichserves as a further means of regulating the flow of airthrough the" apparatus, the main adjustment of this current of air beingcontrolled by the speed of the motor 15. The fine particles will bedelivered into a settling chamber 4 which is of such a size that thevelocity of the air current will be reduced thus allowing a settling ofthe material ,in suspension. As hereinbefore stated this chamber isprovided with spouts 9 for removing this settled material which will beof a gradually diminishing size further along the settling chamber fromthe inlet. Should the material withdrawn from any one or more of thesespouts be oversizethe same may be delivered to the conveyor 7 andreturned to the grinding unit and if the material so large volumes ofair can be admitted through an adjustable air inlet opening 16 at lowervelocity when fines are required and in the opposite ratio for coarsermaterial; and it will therefore be seen that this process is aclassifying process in direct connection with the I Cgrindlng mediumcapable of delivering size claims.

particles from the grinding element. Another feature of my invention notheretofore mentioned is that the filtered air is not returned to thegrinding unit but is discharged into the atmosphere. Fresh air is drawnin through the opening lfi and takes up the finely ground particles assoon as created, the size of the particles held in suspension dependingupon the velocity of the air current, thus preventing any cushioning ofthe unground material within the grinding element. The velocity of airthrough the apparatus is regulated by the speed of the motor and also bythe size of the adjustable inlet opening 16.

My process Is Well adapted for handling ractically all dry groundmaterials such as ne black, cement, feldspar, gypsum,graphite,-limestone, marble dust, phosphate rock, shale, talc, igmentsand all kinds of natural and artificial abrasives.

It will be clear that I have provided a process which will accomplishthe objects of the invention as hereinbefore stated, and it isunderstood that my process is to be limited only in accordance with theappended Having thus described my invention, what I claim is I 1. Theprocess of reduction of finely divided material which consists ingrinding material. in a grinding unit, removng the fines from thegrinding unit by means of a current of fresh air of low velocity andlarge. volume before all the material has been ground to its finestcondition therein, pass-" ing the fines through a settling chamber andreturning to the grinding unit the oven sized particles and passing thesized particles through an air filter without the return of the air usedas the conveying medium to the grinding unit. a

2. The process of reduction of finely divided material which consists ingrinding coarse material in a grinding unit, removng the fines from thegrinding unit by means of a current of fresh air of low velocity andlarge volume, delivering the fines to a settling chamber, withdrawingthe fines still in suspension from the settling chamber and passing thesame through a filtering chamber and discharging the air into the atmosphere.

3. The process of reduction of finely diminishing velocity towards theoutlet and 76 passing the same first through a settling chamber-and thenthrough a filtering chamber without the return of the air in closedcircuit to the grinding unit.

4. The process of reduction of finely divided material which consists ingrinding coarse'material in a grinding unit, removing the fines from thegrinding unit as soon as formed and assing the same first through asettling cham er and then through a filtering chamber by means of acurrent of fresh air of gradually diminishing velocity towards theoutlet without return of the air in closed circuit to the grinding unitand discharging the air used as-the conveying medium into theatmosphere.

5. The process of reduction of finely divided material which consists ingrinding coarse material in a grinding unit, removing the fines from thegrinding unit as soon as they are formed by means of a current of air,passing said current of fresh air of low velocity and large volumethrough a settling chamber and then throu h a filterin chamber anddischarging the filtered air 1nto the atmosphere and returning to thegrinding unit the over-size particles independent of the flow of theair'used as the conveying medium.

6. The process of reduction of finely divided material which consists incrushing coarse material in a grinding unit, with drawing the fines fromthe grinding unit by.

means of a current of fresh air of low velocity and large volume andpassing the current 0 air through a settlin chamber and then through afiltering cham r and dischar g the conveying medium into the atmosp ereand returning the over-size articles to the grinding unit independent 0the flow of the conveying medium. v

7 In an apparatus of the class described, a grinding unit, a settlingchamber connected with said grinding unit, a filtering chamber connectedwith said settling chamber and a fan connected with said filteringchamber anddischarging directly into the atmosphere, said grinding unithaving an openin therein communicating with the atmosp iere, means fordelivering material to said grinding unit, means for operatingsaid fanto cause fresh air to be drawn in through said opening in the grinding.unit and delivered successively throu h said settling chamber andfilterin cham er and dis charging into the atmosp ere.

lbs

8. An apparatus as set forth in claim 7 having means for varyingthevelocity of the having-means for returning-to the grinding conveyingmedium whereb to remove difunit the oversized particles separated in theferent size particles from t e grindin unit. 39 settling chamber, saidmeans being inde- In testimony whereof, I hereunto a my 5 pendent of thepath of flow of the conveysignature.

ing medium.

9. Anapparatus as set forth in claim 7 I W. V

